Venetian blind tilting mechanism



June 17, 1941.

HHLCOHN VENETIAN BLiND TILTING MECHANISM Filed Oct. 28, 1940 INVENTOR.

HMROLD -L COhM/ m ATTORNEY Patented June 17, 1941 VENETIAN BLIND TIIlTING MECHANISM Harold J. Cohn, Los Angeles, Calif., assignor to Automatik Venetian Hardware Corporation, a corporation of California Application October 28, 1940, Serial No. 363,149

11 Claims.

My invention relates generally to hardware used in the manufacture of Venetian blinds, and more particularly to that part of the hardware which tilts the slats of the blind to admit or exclude light.

In nearly all types of Venetian blinds, it is desirable to be able to rotate the slats about a horizontal axis which extends lengthwise thereof, in order that air and light may be admitted, or

- excluded. With the customary type of blind, this is usually accomplished by providing a cord controlled mechanism in which, by pulling on one cord, the slats are rotated in one direction, while by pulling on the other cord they are rotated in the opposite direction. Such cords are unsightly, awkwardand inefiicient, and in my copending application, Serial No. 345,890, filed July 12, 1940, I have disclosed a Venetian blind in which all cords, whether for tilting or lifting the slats, are eliminated. However, I believe that the cordless tilting mechanism described and claimed in this application is in several ways superior to that disclosed in my previous application, in that it is more easily assembled and operated.

The major object of this invention is to provide a cordless tilting mechanism for the slats of Venetian blinds, and particularly for Venetian blinds of the type disclosed in my said copending case.

It is another object of my invention to provide such a mechanism which is simple in construction and positive in operation.

It is a further object of my invention to provide such a mechanism which is easily operated, yet which securely retains the slats in their selected position.

It is still another object of my invention to provide such a mechanism which may be adapted to work with wooden or metal slats, or slats of any other material, having any type of balance.

These and other objects of my invention will become apparent from the following description Referring now to the drawing and particularly to Fig. 1 thereof, it will be seen that the letter A generally designates a Venetian blind which is mounted in a window casing B. Near the top of the casing B, a shaft l 0, supported by brackets l I and attached to a spring motor I2, is provided with pulleys l3 on which lifting tapes M are designed to be wound. Firmly attached to the brackets II are clevises l5, extending below the pulleys l 3, preferably with one arm of each clevis on either side of the corresponding pulley. Journaled in the clevises [5 are trun'nions I9 supporting rockers IE, to which are attached ladder tapes I! supporting slats I8 of wood or metal. The construction and connection of these parts, together with the operation of the lifting mechanism, including the spring motor l2, the shaft Ill, and the pulleys l3, are shown in the drawing and are described in detail in my aforementioned copending application, and form no part of the present invention.

In place of the tilting mechanism disclosed in my previously mentioned application, I now prefer to use the form shown herein which eliminates the need for springs with their attendant inconveniences and disadvantages, and which provides a more easily operable mechanism. In this form of tilting mechanism I attach a ratchet plate 20 to one side of the rocker 16, the plate being provided with a hole 2| through which the trunnion l9 may pass. The lower portion of the plate 20 preferably conforms to the shape of the rocker I6, but the upper edge is given a generally arcuate shape with the axis of the trunnion l9 forming the center of the curve.

In this curved edge I form teeth 22, of a special shape to be described hereinafter, adapted to be engaged by a gravity pawl 23. The pawl 23 is pivotally attached to the clevis l5, and likewise has a special shape to be described in detail later. However, without these detailed descriptions of the ratchet teeth and the pawl, it will be seen that the two cooperate so that when the rocker- IB, and with it the slats l8 of the blind, are turned to any predetermined position, the pawl 23 will engage the corresponding tooth 22 and hold the ratchet plate 20 against further rotation.

Turning now to the ratchet plate 20, it will be seen that the teeth 22 thereof are shaped so that they in effect point toward the front of the blind, an upwardly extending projection on the forward edge of each tooth giving this appearance. Starting from the root circle of the teeth 22, the rear face of each tooth consists of a straight portion 25 which extends upwardly and forwardly to a circular section 26, the straight portion 25 being tangent to this circular section. From the circular section 26, the face of the tooth extends forwardly along a line 21 which is tangent to a circle smaller than the circle forming the section 26, but concentric therewith. The forward face 28 of the tooth is tangent to the rear side of the hole 2I through which the trunnion I9 passes, and all intersecting straight portions of the tooth profile are connected by fillets.

The pawl 23 which engages the ratchet plate 20 is pivotally attached to the clevis I5 at a point substantially vertically above the trunnion I9, and at a suflicient distance above the latter so that the pawl will rest on the ratchet plate with its upper forward end slightly below the axis of the point of attachment. To insure positive engagement, the pawl 23 is provided with aholding tooth 36 on its lower surface near the forward end, the tooth 36 having its forward face shaped complementally to the rear face of the ratchet plate tooth 22. By forming both of these surfaces as arcs of circles, a slight variation in the location of the pawl 23 with respect to the ratchet plate 26 will still permit their respective teeth to mesh properly and positively.

So that the pawl 23 may be easily disengaged, I provide a tail portion 3I on the pawl extending rearwardly from the point of support and partially counterbalancing the forward portion having the tooth 30. This permits the' pawl 23 to in effect float over the teeth 22 of the ratchet 26 whenever the latter is rotated rapidly, while at the same time permitting the pawl tooth 30 to engage a tooth 22 of the ratchet when the latter is moved more slowly.

The need for the upwardly extending projection on the forward edge of each tooth 22 may now be appreciated, since it is this projection which throws the pawl 23 upwardly so that it will ride over the adjoining tooth. By providing this projection with a rear face which has a relatively steep slope, an upward motion will be imparted to the pawl 23 which will cause it to remain above the teeth 22 longer than if no such motion were imparted to it.

The rear side or face of the pawl tooth 30 is cut at an angle and positioned so that it will engage and ride up over the next ratchet tooth to the rear when the ratchet is rotated forwardly. Thus it becomes a simple matter to rotate the slats I8 and rocker I6 so that their forward edges are moved downwardly. However, since the forward face of the pawl tooth 30 bears firmly against the rear face of a ratchet tooth 22, the slats I6 and rocker l6 are locked against rearward rotation, and hence it is necessary to rotate the rocker and ratchet forwardly a slight amount so that the pawl tooth will be raised by the ratchet tooth in back of it. By then quickly rotating the rocker rearwardly, the pawl 23 will be thrown upwardly as each ratchet tooth 22 passes beneath it, permitting the slats I8 to be rotated to a position with their forward edges raised.

This method of disengaging the pawl 23 from the ratchet plate 20 works satisfactorily for all positions of the slats I8, save when they are in the position with their forward edges farthest down. In this position, the slats almost touch each other, and there is not suficient room for them to move as they would have to if another tooth were placed at the rear end of the ratchet 2D. The pawl 23 must be raised, however, and to accomplish this I provide a lifting tooth 35 on the pawl in back of the holding tooth 30, The lifting tooth 35 is shorter than the holding tooth 30, so that it does not touch any of the teeth 22 of the ratchet as they pass beneath it. To engage the lifting tooth 35, I provide a lifting member in the form of a projection 36 located in back of the last tooth 22 of the ratchet 20. This projection 36 extends above the addendum circle of the teeth 22 and is located so that when the holding tooth 30 of the pawl 23 bears against the rearmost tooth 22, any forward rotation of the ratchet 26 will cause the projection 36 to engage the lifting tooth 35 and thus raise the holding tooth out of engagement with the ratchet tooth 22. By providing the rear face of the projection 36 with a portion having a steep slope, the pawl 23 will be given an upward movement similar to that which it receives from the teeth 22, and hence the pawl will float over to the top of adjacent tooth 22 where it will receive another upward thrust. In this way only a very slight movement of the slats I8 is required to disengage the pawl 23 from the ratchet 22.

Since the rocker I6 will normally be pivoted at a point midway between its rear and forward edges for reasons of balance and to provide a sufficient lever arm for rotating it by means of the ladder tape II, only a small force is required to rotate the slats I8 forwardly. Consequently the slats may be accidentally displaced from position quite easily. To overcome this disadvantage, and also to provide means for insuring the rapid and positive rotation of the slats I8 when so desired, I provide a crank arm 40 at one end of each trunnion I9, on which is eccentrically mounted a counterweight II. The crank arm 46 is preferably positioned, as shown in Fig. 4, so that it urges the rear end of the rocker I6 downwardly, and this in turn causes a tooth 22 of the ratchet plate 20 to bear against the holding tooth 30 of the pawl 23 with a certain amount of force. As a result, the slats I8 are securely locked in position, while at the same time the counterweight aids in rotating the rear edges of the slats downwardly when it is desired to do so. This increases the speed of rotation and prevents the pawl 23 from engaging the ratchet 26 before the slats I8 have reached the desired position.

I have found that the balance of a Venetian blind constructed as herein described will vary in accordance with the material used for the slats and also with their shape. As a result, I have found that one amount of counterbalancing is necessary for wooden slats, another for metal slats having an upwardly convex surface, and a third for metal slats having an upwardly concave surface. To avoid the necessity of furnishing three different counterweights with each set of hardware, I provide the counterweight II with an eccentrically located hole 42 to receive the crank arm 40; and by thus changing the length of the lever arm and the position of the center of gravity, I am able to provide the proper amount of counterbalancing for the particular installation. In this connection, I prefer to make both the end of the crank arm 40 and the hole 42 into which it fits, square, so that adjustment is simplified and chances for error are reduced to a minimum.

To operate my improved tilting mechanism, I provide a tab (not shown) of any convenient form but preferably similar to that shown in my copending application Serial No. 345,890, attached to the forward side of one of the ladder tapes I1. There is normally but one ratchet 20 and pawl 23 on each complete blind, but the tab may be placed on any of the ladder tapes I! since the movement of that tape is sufliciently transmitted by the slats Hi to the other tapes and rockers by reason of the counterweight and balance of the blind. Lowering of the forward edges of the slats. I8 is accomplished by merely pulling down on the tab while to raisev them a quick downward pull is given to disengage the pawl 23, and the tab is then quickly lifted so that the counterweight and the weight of the rear edges of the slats will pull the rear end of the rocker it down. When the slats have reached the desired position, the rotation of the rocker is stoppedand the pawl 5.- A device as described in-claiin 4, in which said ratchet teeth are shaped so that the forward edges thereof may bear against said pawl and disengage it from said ratchet.

6. A device as described in claim 4, in which said counterweght urges said ratchet in a direction whereby said pawl engages and holds said ratchet.

23 drops into engagement with the appropriate tooth of ratchet plate 20.

It will thus be seen that I have provided an improved cordless tilting mechanism for Venetian blinds which is quickly and easily operated, but which nevertheless securely retains the blind in any predetermined position. While the preferred form I have described is fully capable of obtaining the above results, variations of form and arrangement of parts are possible which in no way depart from the spirit of the appended claims, and all such equivalents are intended to be included in these claims.

I claim as my invention:

1. A cordless tilting mechanism of the class de scribed, which includes: a clevis; a rocker pivotally mounted in said clevis, and provided with a ratchet plate; a pawl pivotally mounted above said ratchet and adapted to engage the teeth thereof; and a counterweight adapted to urge said rocker and said ratchet in one direction.

2. A device as described in claim 1, in which said pawl is adapted to be disengaged from said ratchet by the movement of said ratchet against the urging of said counterweight.

3. A device as described in claim 1, in which the teeth of said ratchet have an upward projection'on an edge of their outer faces whereby said pawl is thrown upwardly upon rapid motion of said ratchet.

'7. A device as described in claim 4, in which said ratchet teeth are shaped so that the forward edges thereof may bear against said pawl and disengage it from said ratchet, and in which said counterweight urges said ratchet in a direction whereby said pawl engages and holds said ratchet.

8. A tilting mechanism of the class described which includes: a clevis; a rocker pivotally mounted in said clevis and provided with a ratchet plate; a pawl pivotally attached to said clevis above said ratchet and adapted to engage the teeth thereof i and alifting member adapted to engage said pawl and disengage it from said ratchet when the latter reaches one end of its travel.

9. A device as described in claim 8, in which said pawl is provided with a holding tooth adapted to engage said ratchet, and with a lifting tooth adapted to be engaged by said lifting member, and not by other teeth on said ratchet. 10. A device as described in claim 8, which is provided with a counterweight adapted to urge said rocker and said ratchet in. one direction.

11. A tilting mechanism of the class described which includes: .a clevis; a rocker pivotally mounted in said clevis; a ratchet plate attached to said rocker; a pawl pivotally attached to said clevis and having a holding tooth adapted to engage said ratchet plate, said teeth having a rear face adapted to be firmly engaged by said pawl, a projection on their outer faces adapted to move said pawl away from said ratchet when the latter is rotated, and having their forward faces adapted to bear-against said pawl and disengage it from said ratchet; a lifting projection on said ratchet: a lifting tooth on said pawl adapted to be engaged by said lifting projection to move said pawl away from said ratchet when the latter reaches one end of its travel; and a counterweight adapted to urge said ratchet in a direction whereby said pawl engages and holds said ratchet.

HAROLD J. COHN. 

